Apparatus for communication systems



R. H. BROWN APPARATUS FORUC OMMUNICATION SYSTEMS Feb. 5, 1946.-

' 2 Sheets-Sheet 1 Filed Nov 3, 1944 l1\ VENTOR I .ZZobemEBrowzz.

Feb. 5, 1946. R. H. BROWN I APPARATUS FOR COMMUNICATION SYSTEMS 2 Sheets- Sheet? Filed Nov. 3, 1944 I v INVENTOR Rober Ema/12.

BY 319 f'ATTORNEY Patented Feb. 5, 1946 Y APPARATUS'FOR COMIWUNICATION V SYSTEMS Robert 11. Bath, Westview, Pa. assignor to the Union Switch &1 Signal Company, Swissvale.

la.,'a corporation ofPenns'ylvania Application November 3, 1944, Seri e g .10 Claims. My invention relates to apparatus for"cm-' munication systems, and 'more' particularly to calling apparatus fortelephone systems."

In communication systems where a central of: fice is connected to a plurality of stations through a common transmitting channel a calling means is provided. Often such calling means must be unique because the transmitting channel'may be used for several different-systems. For example,

in railway communication a single pair of linewires may serve as a train dispatchers telephone circuit, a telegraph circuit, and as a centralized traflic control line circuit. In each of such circuits the current used is peculiar to'z the use. :For exanipleQthe centralized trafflc controli circuit may use coded direct current of the time 'codetype 'and'the Office operator governs signaling devices at each of several'stationsaccording to the code transmitted- In such icentralized .traflic.

control systems facilities are provided for a memis provided. Th conventional magneto ringing for a calling means is not permissible-because of the nature of the:other circuitsusingthe same" pair of line wires. 0

Accordingly a feature ofimy invention-isthe provision of improved ng means for 'com-r municationsystems, 1 v:

Anotheryfeature of my invention is the provision of novel voiceoperatedcalling means for communication systems. A

Still another feature of my' invention is the provision of calling means incorporating a novel circuit arrangement to operate the :calling indicator' until the call is acknowledged;

Again, a feature of my invention is the pro-.- vision of apparatus of the type here contemplated incorporating novel meansto d'eionize a gas tube. 7

Other features, obiects and advantages of' 'my invention will appear as the specificationprogresss. l

The above cited features; obiectsland 'advantages of my invention are attained byproviding at the oflioe a calling unit whichlincludes a selec tive circuit, an electrontube, a relay; a potenti ometer, adelay action means and a call bell'orindicator, together with novel circuits; Theoflice is also provided with a.propersourceofcurrent; The selective circuit of the calling unit'is nor---' mally connected across 'th'e line circuit and is" tuned to pass the voice frequencies or to pass a preselected band of frequencies. Theelectron (Cl.179- -84) I v tube is preferably on controlled ionization type and it is provided with ananodecircuit which includes the oflicesource of power, aback con-" tact'and a'winding of anoflicerelay; Thus when the tube is fired and the associated relay-is energized and picked up; the picking 'up of-the relay opens the anode circuit and the tube is deionized. The potentiometer is connected across the current source and the controlelectrodeor 10 I the tube is connected to i an adjustable "terminal of the potentiometer to provide a normal'bias voltage for'the tube; The parts are proportionedk so that the normal anode voltage and the normal I 'bias voltage for the the tubes are insufficient to li-firethetubes. T v The control electrode is also connected'to-the selective circuit and'the higher values of the voice.

or calling frequency current drive the control electrode in a positiv direction sufliciently 'tos' fire the tube. In one form of the invention the: delay action means includes a capacitor anda resistor, the capacitorbeing connectedacross the winding of the relay and theresistor.being-interposed in the anode circuit. I Whenthe tube is. first fired the capacitor is charged at a ratefpre determined by the value of theresistor. When the capacitor becomes charged current then flows in therelay winding sufii'cient to energize rand pickup the relay. Thepicking up'of the relay opens the anode circuit and deionizes the tube:

The capacitor now discharges through the relay winding and retains therelay energized and. picked up for aperiod. After the capacitoris discharged the relay releases to reclose the anode circuit. In this way the relayis provided both with a slow pick-up'period and' aslow 'torelease period. The call bell or indicator is controlled through "a front contact of. the relay: and is thus sounded during the slow release period of the re-= 40 lay." When the relay is released and the anode: circuit of the tube reclosed, the tube is not again firedunless the voice frequency/current is. re-. peated. By use of a manually operable'switch and overlapping contacts'of the relay analter -Q native bias circuit is arranged for the; tube :and. the tubeonce fired and the relay picked up'the' tube is provided with an'additional bias voltage. which is sufiicient to fire the tube in responsexto; the normal anode voltage. Thus this alternative.

arrangement provides that once. the relay 1 is picked up in response to'the tube-being fired due to the presence of a voice frequency current, the relay is alternately released and picked-up and the call bell is intermittently operated until the callisacknowledge'd by theoflice operator'taking;

1 system.

In each of the two views like; references-clean 1 steps to open the anode circuit of the tube. When a relatively long delay period isrequired, a second relay is included in the delay action means.

form of apparatus" embodying my invention when used with a railway centralized traflic control acters are used to designate similar parts.

Y and Z designate line wires which extend be.

and as the line circuit of a centralized tralfic Referring to Fig. 1, the reierence characters time. with winding 15 of relay LR.

Ishall describe two forms of apparatus em bodyingvmy invention, and shall then'point out p the novel features thereof in claims The accompanying drawings Figs. 1 and 2 are 1 diagrammatic; news showing a menace, asec nd 3 tween two'spaced locations of a railway tepid 1 vide a transmitting channel between such lo'cations. These two line Wire's: may be. used inaa i dispatchers telephone circuit, a telegraph circuit! 1 control system; It. istobe understood; car-course; 1 tiiaitmy' invention is not limited. to it pair: of; line 3 1 wires in several facilities: amt thel-ine wires 1 Y maybe used. for telephone communica- 3 tiorrozirly. In, order-to not unduly complicatethe drawings; the use. ofilinewiresYand Z fior'tele phone communication. in connection with'a cen 1 tralizedi trams: controlsys-tems only is shown.- The omce ofisuch a system indicated by a, dash and,

1 dot rectangle: OF and. one station of the system.

1, is. indicated'bry a. dash and; dotarectangle ST; v

I Only theone station S'E is. shown. since one sta station ST is provided wit-ha, telephone set .1 eluding a transmitter 2, and a receiver .3; which tlon: is suafificient to fully illustrate-the invention, 1

The offic on is provided with a, calling unit 1 indicated; asa whole by a dotted rectangle CH 1 and a battery Brl together with a telephone: set comprismga transmitter 38; and a loud speaker 1 and a switching hey KS.

includes a transformer Tl;

1 ages time Vi, a relay- LRt: a potentiometer RI. 3 acall bell (1H, a. delayaction. means; comprising capacitor 621 and a resistor R2; and three switches JSWII, and SW3,- asessential elements. f The ofiizce battery BI .is preferably of; thewsplit battery type of a prdnerpreselecteclvoltage which maybe forexample; oil the order of; 11m voltsl, 51???? in is to" be understood, of course, that other sources of direct current may be used.

The calling unit CU is provided with terminals for connection of its elements to" the outside air ci i'itsl aml'such will be: referred to as? the apparatus isd'escribei.

5 The line wiresY and Z: are connectedthrmigh lwires 1 to terminals LI! and L2 or th e'unit and across which terminals- 9: primary winding 8 of transforms)? It is connected through; consioo itact members 5 andfll of switch when that switch is closed; Primary-winding it is. prefer,

ably. arranged in two portions; and a capacitor Ct interposed between the; twoportions. The. @apaoitor: Of andv the \izinidingi it are; proportioned to form a circuit tuned. to pass the voice frequerr cies or to' pass a'preselected bandof the voice frequencies. example, this circuit including capacitor Cl: and. winding 8% may Hie timed to pass a voiceireqnency banal extendmg from 600: to 15260- cyclesgper second, or it may be timed. to pass ttbdrid or only a] few cycles in width;

? he of any one of several difierent sand is shownas a; cold cathode gas tube a ving an'anode 65, a. cathode Wanda control electrode 25. Tube VI is supplied with power from battery B! through an anode circuit, and

,which anode circuit extends from positive terminal Bl ll) of battery BI through wire I I, terininal BP of unit CU, contact member l2 of switch SWI when closed, transfer contact 13 and back contact 14 of a,continuitytransfer type of coner "relay winding; ('5 of relay LR, resistor the negative. terminal. NI IU of the battery. It is to b enotedlthat capacitor C2 is connected in mul- A bias volta e is applied to the tube VI from battery Bl; 'm this -connection a mid terminal 0 of battery BI is connected to terminal BL of the unit CU and the potentiometer resistor RI is connected across the; terminals: BP and BL through backxcontact M. and. transfer contact-.13 of relay The. control electrode. Zioitube Vi is colmectedato an adjustable terminal 26 of resi'stor Bl through secondary winding 2.1- :of transa former T l; and resistor 28." mam be seen, therefore; that controlelectrode 25 is made positive. inpotential; with respect tocathode I! by a voltage preselected by the position of, the adjustable, tee-- minali zfi: The parts areproportioned so that the voltage supplied to. the control electrode; is nor mallyainsuificient to cause a tube :to baflred due. to the voltage supplied to. the, anode circuit; I

The call: bell; GB is energized by power from battery Bl, the circuit: fortl'ie bell including ter minal B-HO, ,wire. It; terminal BB, contact mem beri l2: or switch SW t, transfer contact l3,- fren l contact 3| 0i relay LR; bell GB; and thence. to thenegativei terminal NIH.v through the same comiections; tracedfor the-anodecircm't from cathode H of tube Vt. Thus thebell GB is ener gized and sounded whenever thearelayis pickedswitch SW3 governs an alternative bias, circuit: for'thetube, and by which circuit tube Vl: is providerr with an additional positive biasvoltage. This alternative circuit can be traced iromfposl tive; terminal Bi I c throng-h It, terminal BP,

contact membert2 or switch SW l1, wire. 32', switch SW3, transfer contact 33 and frontcontact 314 of a continuity transfercontact of relay LR and resistor n-to control electrode 25.- Since cathode I1 is connected to the negative terminal Nil-.0 or battery Bl through the connection traced hereinbetore, it follows. that the control electrode 25 is provided through this alternative circuit with.

a positive biasvoltage with respect to the cathodesubstantially equal to the full voltage of battery IBt l lormall y, that is; when no calling vol-cecurre'ntis applied to the transmitting channel, the tribe:

Vt is non-conductive, relay'LR is released. and the call bellGR; is: silent: An operator at station ST wishing to call the oilice operator wouldremove the; receiver 3 from the hook switch; and

speak an appropriate: word or phraseinto the transmitter" 2; word-v or phrase is selected to; contain voice irequencies such that current a in the selective circuit including winding 8- 04E transformer 'I t of the callingunit GU, and a correspondingelectromotive force? is induced insecondairy winding 21' or the transformer: 'Ilhe' positive half cycles or. such; electromotive force induced in the-secondary winding Zt are additive to" normal bias voltage 02- tube: Vt and:

control electrodes is driven:.in the .positive' directionfsuiiicientxtoffire thertube. At the start Of'TthB conductive condition of tube V I, capacitor C2. chargeszthrougnresistor R24 ,zand this charge of :currenthcauses a voltage drop across resistor .R2"and' the voltage across thewinding I of relay operator that the operator at statio-nST wishes of relay LR fails to fire thetube' unless'thecalling current continues or is repeated.

In responsetosuch calling, theofliceoperator would remove the transmitter 30 from the hook or insome other manner open the keyswitch KS to close contacts3533 and 31-38 and open contact 2I--22. The closing of contacts 35-36 and 3'I--38 connects the ofilce telephone set across the line wires'and telephone communication can be carried on between the ofiiceand the station. The opening of contact 2I-'-22 opens the anode circuit for the tube VI and-the calling unit is made inactive duringsuch telephone communication.

Tointermittently-operate we call bell CB, the switch SW3 is closed. Under this condition a calling current applied to transformer TI serves to fire tube VI and pick up relay LR in the manner previously explained. When relay LR is picked up to close front contact 33-34, the alternative bias voltage is applied to the control electrode, and which alternative bias voltage is sub.- stantially the full voltage of battery BI, and is much higher than the normal vias voltage ap-v plied to the tube through the potentiometer RI. When relay LR is picked up to open the back contact the tube VI is deionized due to the opening of its anode circuitthe same-as before. Relay LR is released subsequent to the discharge of the capacitor C2 and the anode circuit i reclosed at back contact I4 before the alternative bias circuit for control electrode 29is opened at front contact 33-34 of the relay due to'the continuity transfer type of contacts. The higher bias voltage is suflicient to fire the tube when the anode circuit is reclosed and thus the operation of reenergizing the relay LR is repeated and the call bell CB is again sounded. Such intermittent operation of relay LR and bell CB will berepeated over and over again until the oiiice operator takes steps to answer the call by operating the key switch KS.

It is to be noted that if the direct current source is of the type that has no midterminal 'C, the potentiometer resistor RI would be connected between'the'terminals 'BP-and J2.

Referring to "Fig. 2, the line wires '3! and -Z extend'between an 'oiiice OF and a station ST to form a transmitting channel through which telephone :coinmunication can'='-:be:efiected; :The

"station. sTzandiofiice" OF: areiiprovided :with' telephone equipmentvwhichris'the same paszthatsof Fig-.1, exceptfor the calling uniteand aidescripation' of only thisvportion 'of; apparatus :of Figl'i'z is required. r

fAlsoein'f-Figgzthe oifice: is provided iwithr.a:bat

fteriyi B2 .1of1-10 volts; and arbatte'rysB3rof ;16"volts. It. is: toxbe.runderstoodphowever, that one z'battery only. or; other. source; ofirpoweri caniibe used.

:Thecallirigmhit of Fig. 211s fdesignated aaa wholefzby. a dotted rectangleiCUI. This calling unitt CU I tissimilar :toithe calling unit: CUof .iFlg. .1,- excepti it is provided with a'sisecondi'relay 13R and a capacitor: C3 .as a'n'iadditional- 'delay 'action rneans. =Also,i;the' call bellzCB- =18 of "the-single strokeitype and I an. indicator lamp iLP. isensed-to provi'd'ee'ai continuous indication. I

':It is: believed the apparatus .ofFig'fZ will best beunderstood from a description of its operation.

Normally; that is, when no :xcalli'ng current .is applied to the vline lWilfS"Y' and. Z,"the tube VI is noneco'nductiv'e; relays'LR and BR 1 are "released, indicator lamptLPr iswdark and the bell 1 GB is silent. plied-.to .the anode of tube ,VI byxarcircuit extendingltf rom; terminal 'BIIB of battery ;B2 through backs contact ill-of; relay LR, windinge I 5 of that relay, resistorrRZ, anode-:IG. and tubeispace tofcathode I I of tubeiV I- :and thencei to iterminal NII'E! of :b'atter y BZ. -Also a.bias :voltage'is applied to -control= electrode i25: of' tube VI from intermediate terminali-2fi of.:the potentiometer'resistoriR I throughsecondary windingw'fl of transformer TI and resistor 28. Theiparts1areiproportioned for tube VI to'vbe normally non-:con-

ductive; r I

When a calling current having Ithexpreselected frequencies is applied to theiline' circuit, current flows'in the tuned circuit including capacitor .CI and 1 primary winding 8' oftransformer TI. '1 have 'foundthat such 'rcallin'gcurrent maybe created by blowing or whistling-into-the microphone 2 at the station ST. In either case the callingcu'rrent will have a frequency band to which the selective circuit of the calling unit can be tuned and current surges created by lightning and other conditions are of such short duration that they cause'little or noresponse inthe calling unit. The effective calling current-flowing in the selective circuit induces a corresponding voltage in seoondary winding 21 andthepositive half cycles of such voltage drive the control electrode25 of tube VI in the positive'direction sufficient to fire the tube. With tube VI concapacitor C2 is preferably'relatively small, and.

' thus when'relay LR is picked up opening'back contactdi'l, the anode'circuit'of "tube VI isinterrupted with the result relay LR is immediately released.- With relay LR released, the anode circuit is reclosed andthe tube VI is again fired.

Relay LR-is thus operated as long asthe calling current continues to flow. Such operation of relay-LR to recurrently close 'front contactill causes capacitor C3Jt0 receive charging pulse Under this'normal condition jpowe'r is apeach time contact. H is closed and to discharge throughvthe winding of relay BR each period front contact 4| is open. 7 The parts are so pro- 1 portioned, that the charge supplied to capacitor C3 is greater than the discharge" The result is that capacitor C3 soon becomes charged to a voltage equal tothepick-up voltage'of relay BR and that relay picks up. With relay BR picked up it'is retained picked up'through astick circuit extending from terminal B16 through. front contact'145 and winding of relay BR, and resistors 43fand 44 to terminal NIB. During the intervaL .relayrBR' is picking uplcurrent flows from terminal BIG th'rou'gh' front contact 46, transfer contact'41and back contact 48 of a "anditerminal NW, and the. bell GB is operated for a single stroke." With "relay BR picked up the lamp-LP is supplied with current from termirialBlS through-front contact 46 and transfer contact 41 oflrelay BR andlamp LP to terminal NIB." Furthermore, when relay BR is picked up anialternative bias circuit for tube VI is completediand relay LR is' operated notwithstanding the calling current has terminated. With the sounding of the bell CB and the illumination of lamp LP the; oflice operator knows telephone communication is desired and he removesfhis telephone set from the hook operating the switch KS to'connectthetelephone set with the line circuit. The opening of contact 22 or switch KS opens the connection of battery B3 to i terminal BIG and relays BRand LR of the unit CU'l are restored totheir normal condition extinguish'lamp LP. V Apparatushere disclosed has the advantages that calling is effected with only the telephone set required at the station; the oifice apparatus is sensitive 'to voice current, the gas tube is powered from a-direct current source,and the ofilce call indicator "can be operated once in response to the call or can-be made to intermittently respond to the call until the call is acknowledged. Also the apparatus can bearranged in a single calling unit. Although'Ihave herein'shown and described buttwo forms of apparatus for communication ystemsembodying my invention, it is understood that various changes and modifications may be Jmade therein within the scope of the appended claims without departing from the spirit and scope of myinvention;

claim is: 1 l l 1., In apparatus for communication between an officeand a station connected'by a transmitting channel, the-combination comprising; an oflice source'o-f current and an, ofiice calling unit; said unit including a selective circuit, a relay, an elecing, a source of current and a calling unitziat said distant point; said unit including a tuned circuit, a relay, a gas tube and a call indicator; said tuned circuit connected to said channel; saidgas tube provided with an anode circuit connected to said current source and including a back contactand a winding of said relay, said tube also provided with a control circuit'connected to a control electrode of the tube and coupled to said tuned circuit to fire the tube in response to current of a fre= quency to which the-tunedjcircuit is responsive,

supplied to said channel atsaidcontrol point, and

said call indicator governed through-a front con- 7 tact of said relay.

continuity transfer contact of relay BR, bell CB '3. In apparatus for communication between a control pointand a distant point connected by a transmitting channel, the combination com'-- 1 prising, asource of direct current at said distant point and a calling unit having a first pair of terminals connected to said channel and a second pair of terminals connected to said current source; said unit including a selective circuit con- 7 I nected to said first pair of terminals and tuned tov pass a selected frequency, a relay, agastube provided with an anode circuit and a control electrode circuit with the anode circuit include ing a backcontact and a'winding of said relay 5 Having thus described my I invention, what I "relay. I, l, 4. In apparatus forcommunicatlon between an and connected to said second pairv of terminals andwith the control electrode circuit coupled to 7 said selective circuit to fire the tube in response "to current supplied to said channel at saidcon.

trol point of the frequency passed by said selective circuit, a capacitor connected :across said relay winding'to control the .pick up and release of saidzrelay, and a call indicatorconnected to 'a front contact of said current source through a a winding coupled to said selective circuit and a preselected portion ofsaid resistor to provide a normal bias voltage of the control electrode and a control voltage to fire the tube in' response to.

a voice current supplied to aid channel at said station, and a call indicator governed through a front contact of said relay. t.

trontubeand a call'indicator; said selective circuit connected to said channel and tuned to pass a preselected frequencyv band, said tube provided with an'anode circuit to connect said current source .tojan anode-and cathode of the tube and relay, said tube also provided with a control electrode circuit to connect a control electrode and cathode "of the tube to a winding coupled to said selective circuit to control theanode circuit current to pick up fsaid relay'in response to a calling current'of said frequency band supplied to said channel at said station; and said call indicator governed through a'front contact of said relay. l

'2; In apparatus for communication between a control point and a distant point'connected by a transmitting channel, the combination compris- 5. In apparatus for communication between an oflice and astation connected by a transmit ting channel, the combination'comprising, an office source of direct current, an ofiice selective including a back' contact and a winding of said i circuit connected to said channel and tuned to pass a preselected; band of voice frequencies; an office gas tube having an anode, a control electrode and a cathode; an office relay having continuity transfer contacts, an anode circuit for said tube connected to said source and including a back contact and a winding of said relay to energize the relay when the tube is fired, a control electrode circuit for said tube and including a winding coupled to said selective circuit to fire the tube in response to a voice current supplied to said channel at said station, a call bell connected to said current source through a front contact of said relay, and an alternative control electrode circuit for said tube connected to said current source and including a front contact of said relay to recurrently fire the tube subsequent to the firing of the tube by said voice current due to said continuity transfer contacts of said relay.

6. In apparatus'for communication between an ofiice and a station connected by a transmitting channel, the combination comprising, an ofiice source of direct current, an ofiice selective circuit connected to said channel and tuned to pass voice frequencies; an office electron tube having an anode, a cathode and a control electrode; an ofiice slow release relay, an anode circuit to connect said current source to said anode and cathode and including a back contact and a Winding of said relay, a control circuit to connect said control electrode and cathode to a winding coupled to said selective circuit to control the current flow of said anode circuit to pick up said relay in response to a calling voice current supplied to said channel at said station, a call indicator governed through a frontcontact of said relay to indicate such calling current during the slow release period of said relay, and an alternative control circuit connected to said control electrode and cathode through a front contact of said relay and including a bias voltage source effective to control the anode circuit current to pick up said relay, and said last mentioned front contact arranged to overlap said back contact to cause an intermittent operation of said indicator subsequent to said calling current.

7. In apparatus for communication between an ofiice and a station each provided with a telephone set and connected by a transmitting channel; the combination comprising, an office source of direct current, an ofiice selective circuit connected to said channel and tuned to pass voice frequencies, an office relay; an ofiice gas tube having an anode, a cathode and a control electrode; an anode circuit to connect said current source to said anode and cathode and including a back contact and a winding of said relay, a control electrode circuit to connect said control electrode and cathode to a winding coupled to said selective circuit to fire the tube in response to a calling voice current supplied to said channel at said station, a call bell connected to said current source through a front contact of said relay to sound an indication in response to such voice current, and a key switch at said ofiice operable to connect the ofiice telephone set to said channel and to open said anode circuit.

8. In apparatus for communication between an ofiice and a station connected by a transmittin channel, the combination comprising, an office power source means and an ofiice calling unit; said unit including a selective circuit, a first and a second relay, an electron tube and a call indicator; said selective circuit connected to-said transmitting channel and tuned to pass a preselected frequency band, said tube provided with an anode circuit connected to said power source means and including a back contact and a winding of said first relay, said tube providedwith a control circuit connected to a control electrode contact of said second relay to connect said call indicator to said power source means.

9. In apparatus for communication between an ofiice and a station connected by a transmitting channel, the combination comprising, an.

office power source means and an ofiice calling unit; said unit including a selective circuit, a first and a second relay, a gas tube and a call indicator; said selective circuit connected to said transmitting channel and tuned to pass a preselected frequency band, an anode circuit including a back contact and a winding of said first relay to connect said power source means across an anode and cathode of said tube but normally ineffective to fire the tube, a control circuit receiving energy from said selective circult and connected to a control electrode of said tube to fire the tube in response to a calling current supplied to said channel, said first relay being recurrently picked up and released due to such calling current, a capacitor connected to said power source means through a. front contact of said first relay to progressively charge the capacitor by such operation of that relay, said capacitor connected to a winding of said second relay to energize the second relay. when a predetermined charge is built up on said capacitor, and means including a front contact of said second relay to connect said call indicator to said power source means.

10. In combination, a first relay, a second relay,

a gas tube, an anode circuit including a back contact and a winding of said first relay to connect a power source across an anode and cathode of said tube but normally ineffective to fire the tube, a control circuit connected to a control electrode of said tube to at times apply a voltage to the tube sufficient to fire the tube,

said first relay being periodically operated when such control voltage is applied, a capacitor connected to a power source through a front contact of said first relay to progressively charge the capacitor in response to such operation of said first relay, said capacitor connected to a winding of said second relay to energize said second relay when a predetermined charge is built up on said capacitor, and indicating means governed by a circuit completed through a front contactof said second relay.

ROBERT H. BROWN. 

